High purity chemicals used in the semiconductor and pharmaceutical industries require special packaging to maintain their purity in storage. This is especially true for chemicals that react with air and/or moisture in the air. Such high purity chemicals are typically supplied in containers such as bubblers or ampoules.
Modern chemical vapor deposition and atomic layer deposition tools utilize bubblers or ampoules to deliver precursor chemicals to a deposition chamber. These bubblers or ampoules work by passing a carrier gas through a container of high purity liquid precursor chemical and carrying the precursor vapor along with the gas to the deposition chamber.
The containers are typically manufactured as either one-part (i.e., the top cover or lid is not removable from the base) or two-part (i.e., the top cover or lid is removable from the base and can be attached to the base by bolts) containers. The one-part containers have a high degree of integrity, but are more difficult to clean than the two-part containers. Because the top cover or lid can be removed from the base, the two-part containers are easier to clean but are more difficult to seal and reuse. Easier cleaning allows for the reuse of a two-part container beyond what may be achieved with a one-part container. Reuse of containers is important for minimizing costs and also for environmental concerns.
As integrated circuits have decreased in size, so have the dimensions of the internal components or features. As the sizes decreased, the need for more pure chemicals has correspondingly increased to minimize the effect of impurities. Suppliers therefore, must be able to not only manufacture high purity chemicals, but must also be able to deliver them in a container which will maintain the high purity.
The standard materials of construction for these containers shifted from the delicate quartz containers to stainless steel in the late 1990's. See, for example, U.S. Pat. No. 5,607,002. These containers are known in the industry either as bubblers or ampoules and are now routinely constructed of stainless steel, e.g., 316SS. See, for example, U.S. Pat. Nos. 3,930,591, 6,029,717 and 7,077,388.
Further, in most cases, it is necessary to heat the ampoule by some means in order to increase the vapor pressure of the precursor and thus increase the amount of chemical in the carrier gas. It is important to monitor the temperature of the liquid precursor chemical inside of the ampoule to control the vapor pressure.
It is also important to know when the liquid precursor chemical inside of the ampoule is close to running out so that it can be changed at the end of a chemical vapor deposition or atomic layer deposition cycle. If the ampoule should run dry in the middle of a cycle, the entire batch of wafers will be ruined resulting in a potential loss of millions of dollars. It is therefore desirable to leave as little liquid precursor chemical as possible inside of the ampoule to avoid wasting the valuable liquid precursor chemical. As the cost of chemical precursors increase, wasting as little chemical as possible becomes more important.
For two-part high-purity chemical containers to gain commercial acceptance, it will be necessary to develop a more reliable seal. U.S. Pat. No. 6,905,125 relates to a metal gasket such as C-ring gasket to prevent leakage of fluid from semiconductor manufacturing apparatus. High purity chemicals for the electronics industry require leak-tight containers that are able to withstand high vacuum.
It would be desirable in the art to provide an easy to clean, two-part vapor or liquid phase reagent dispensing apparatus which is capable of maintaining high purity of the precursor chemical and also increasing the usage of the precursor chemical in the apparatus, and correspondingly reducing waste thereof.